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Smart stent breakthrough

A "SMART" implant that delivers drugs to targeted parts of the body and controls how quickly they are released into the bloodstream has been developed by Australian scientists.

Experts in nanomedicine at the University of Wollongong say the implants could remove the need for the electronics used in artificial pacemakers and cochlear implants and could revolutionise the way drugs are circulated around the body.

Dubbed "biobatteries", the smart implants build on technology already developed by the university’s Intelligent Polymer Research Institute to create a bioabsorbable stent for use in cardiac patients.

The current generation of stents are made of metal and coated with a tiny dose of a drug that slowly dissolves. The implant is permanent, has a raft of side-effects and makes it difficult to control how quickly the payload is released.

In contrast, the new biodegradable stents, which are made of magnesium alloy, gradually corrode away inside the body, producing an electrical signal that expels the drug from the polymer structure.

The director of the institute, Professor Gordon Wallace, said as the magnesium oxidises, the resulting current reverses the electrostatic charges holding the drug molecules to the stent, releasing it into the bloodstream.

To control the rate of drug delivery, the team coated the magnesium alloy with an "intelligent" biodegradable polymer that slowed its corrosion.

At a medical bionics meeting in Victoria last month, Professor Wallace said the technology could be used in any implant that corrodes, such as titanium hip joints, New Scientist reported.

"Any metal implant will undergo some corrosion when it’s put in the body and this is a new way of harnessing the electricity that comes from the corrosion," he said.

Eventually, the technology could be used to create the electromaterials required to drive bionic eyes, pacemakers, artificial muscles and nerve repairs, removing the need for an external power source.

A spokesman for the Cardiac Society, Associate Professor Andrew MacIsaac, said biodegradable stents would not only reduce the drawbacks and serious side-effects seen in permanent metallic stents, but the gradual release of anti-inflammatory medications could help prevent clotting or damage to the surrounding tissue.